1. Field of the Invention
This invention relates to a drying apparatus which is used in drying liquid droplets coated on a platelike workpiece mainly by means of an imaging or picturing apparatus having liquid droplet ejection (or discharge) heads, and also relates to a workpiece processing apparatus having the drying apparatus.
2. Description of the Related Art
An attempt has conventionally been made to manufacture a color filter and an organic electroluminescence (EL) device by using an imaging apparatus which is provided with liquid droplet ejection heads as represented by ink jet heads. In the above-described imaging apparatus, the following steps are performed. Namely, a function liquid containing therein a filter material and a material with emitting (light-emitting) function is introduced into the liquid droplet ejection heads. Relative scanning is performed between a color filter substrate, an organic EL device substrate, or the like, as the platelike workpiece and the function liquid droplet ejection heads. A multiplicity of pixel regions on the substrate are coated with the function liquid which makes (or serves as) the filter element and the organic EL layer. The function liquid droplets are thereafter dried and solidified to thereby obtain the filter element or the organic EL function layer.
In order to improved the productivity, it is considered to use three imaging apparatuses to comply with the three colors of red (R), green (G), and blue (B), and feed the substrate in sequence into the imaging apparatus to thereby coat the substrate with the function liquid corresponding to each of the colors of red, green and blue. In this case, even if the final drying step for solidifying the function liquid droplets is performed in a subsequent step, the following becomes necessary to prevent the function liquid droplets that have been coated onto the substrate by means of each of the imaging apparatuses, from flowing or from being fluidized on the way of transporting the substrate to the imaging apparatus in the subsequent stage. Namely, a drying apparatus is disposed in parallel with each of the imaging apparatuses. The function liquid droplets that have been coated on the substrate are dried to such a degree as to lose the flowability. Thereafter, the substrate is transported to the imaging apparatus in the subsequent stage.
Although not relating to an arrangement in which the drying apparatus is disposed in parallel with the imaging apparatus, there is known an apparatus in which a hot plate is disposed inside a casing so that a workpiece is mounted in position on the hot plate (see, e.g., Published Unexamined Japanese Patent Application No. 127330/1997). In this apparatus, a plurality of casings each having housed therein a hot plate are held in stack so that a plurality of workpieces can be dried at the same time.
In case the drying apparatus is disposed in parallel with the imaging apparatus as described above, the time required for the drying work is longer by several times the one required in the imaging apparatus. As a result, it becomes necessary to be able to dry more than several workpieces (substrates) at the same time in the drying apparatus.
Here, in an arrangement in which the drying apparatus is made by holding in stack the plurality of casings having housed therein the hot plates as in the above-described conventional example, the apparatus becomes large. It is, therefore, desired to house the plurality of hot plates in a plurality of vertical stages within a single drying apparatus. In this case, however, a solvent to be evaporated from the function liquid droplets that have been coated on the workpiece is likely to stay or remain inside the drying apparatus. This brings about a problem in that the function liquid droplets cannot be dried efficiently.